Yuki Nagato is the quiet alien-human in the back of the clubroom reading books all the time. She is a humanoid created by Data Integration Thought Entity, which is responsible for monitoring Haruhi Suzumiya and the investigation of an unexplained "explosion of data" three years prior to the present story. She has abilities to manipulate her environment and surroundings, or "data" that she refers to. She seems like a quiet person, but if it deals with her mission or anything of her doing, she can be talking non-stop. While she's being interrupted in her reading, she comments that she is only relatively interested in the members of the SOS Brigade and the SOS Brigade itself. Yuki Nagato once in a while is giving hints to Kyon to aid control Haruhi Suzumiya from changing reality the way it currently is. She shows interests in reading and programming computer games.